The present invention relates to a mounting structure for a switch device such as a breaker or an electric leakage breaker.
As an example, an internal structure and a mounting structure of a breaker are described with reference to the following drawings. FIG. 4 is a view illustrating an assembled structure of a breaker. Reference numeral 1 denotes a main body case having a three-piece structure including a lower case 1a, an intermediate case 1b. and an upper case 1c. The main body case 1 is internally provided with a main circuit breaking section 2, a switching mechanism section 3, an over current detecting section 4, a switching handle 5, a power supply side and a load side main circuit terminals 6 and 7, and others. Reference numeral 1d denotes vent slots for the breaking section 2 that are opened in the front and rear surfaces of the lower case 1a so as to correspond to the respective poles of the breaking section 2.
Further, to allow the breaker to be mounted on a support rail laid in a switchboard or the like, the main body case 1 is equipped with a rail groove that fits into a support rail 9 and an engaging slider 8 that projects to the rail groove. Reference numeral 8a denotes an urging spring for the slider 8.
Furthermore, in addition to this rail mounting mechanism, to allow the breaker to be mounted directly on a switchboard or the like using screws without the support rail, an recess portion 1e is conventionally formed in each of the front and the rear surface of the lower case 1a so as to form a screw seat 1e-1, as shown in FIG. 7. The screw seat is formed at a location of the corresponding recess portion in order to eliminate a projection from the main body case 1 to provide compact construction.
Then, to mount a breaker using screws without a support rail, a setscrew 10 is inserted into the screw seat 1e-1 and then screwed thereinto using a screwdriver 11.
The conventional screw mounting structure of the switch device involves the following problems:
(1) The screw hole in the screw seat 1e-1 is opened inwardly of the corresponding end surface of the main body case 1. Accordingly, to mount the switch using the screws, the screwdriver must be inclined during handling the setscrew, as illustrated in FIG. 7. This makes it difficult to tighten the screw, and threads on a screw head may be tore down when the screw is tightened with a strong force thereto.
(2) Further, the setscrew 10 is located at substantially the same height as the vent slots 1d opened in the corresponding surface of the main body case 1. Therefore, a gas ejected from the breaking section through the vent slots 1d is blown against the setscrew 10 when the breaker current is interrupted. As a result, the switch may fail the ground voltage test conducted at an operation site.
The present invention has been made in view of these problems, and it is an object thereof to solve these problems in order to provide an improved switch mounting structure that allows an operator to handle a tool easily and safely upon mounting a switch using screws.
It is another object of the invention that the switch stands the ground voltage test after long usage.
Further objects and advantages of the invention will be apparent from the following description of the invention.
To attain the above objects, the invention provides a mounting structure for mounting a switch device using screws, which is otherwise mounted on a support rail without screws. A switch device comprises a main body case that is provided with a main circuit breaking section, a switching mechanism section and the like internally. The main body case also has slots for inserting mounting plates in a front bottom surface and a rear bottom surface thereof. When the switch device is mounted using the screws, a mounting plate with a screw hole is inserted into a corresponding slot. The mounting plate engages and is locked to the main body case, so that the switch can be mounted by using the screw inserted into the screw hole in the mounting plate (the first aspect of the invention).
Specifically, the slot and the mounting plate are formed in the following manner:
(1) The slot is formed apart from vent holes of the main circuit breaking section that are opened in the front and the rear surface of the main body case (the second aspect of the invention)
(2) The mounting plate has an arm portion extending away from the screw hole, and has a hook-shaped claw portion at a tip of the arm portion. The claw portion engages and is locked to an engaging stage portion of the main body case when the arm portion of the mounting plate is inserted into the slot in the main body case (the third aspect of the invention).
With the above construction, when the mounting plate is installed on the main body case, the screw hole is located away from a sidewall of the main body. Accordingly, when the switch is mounted by using screws, an operator can use a screwdriver vertically and tighten a setscrew in such a way that the operation is not obstructed by the main body case.
Further, since the slot is formed apart from the vent slots in the main body case, a gas from the vent is released away from the mounting plate. Thus, the switch device withstands the ground voltage test after long usage, which is conducted in an actual use state where the switch device is mounted in a switchboard.
The mounting plate of the above structure, which is used as an accessory of the switch device, can be installed on the main body case with a single insertion motion. In the installed position, the claw portion of the mounting plate engages the engaging stage portion of the main body case, thereby preventing the mounting plate from inadvertently slipping off the main body case. Further, by pushing the claw portion from the bottom surface of the main body case to disengage the claw portion from the engaging stage portion, the switch can be pulled out from the main body case. Accordingly, when the switch device needs to be mounted on a support rail later, the mounting plate can easily be removed from the main body case.